1. Field of the Invention
This invention relates generally to the processing of dielectric materials utilizing microwave energy to do so, and pertains more particularly to a system and method utilizing concentrated microwave power for heating, drying, curing and/or deinfesting a wide variety of such materials.
2. Description of the Prior Art
The patent literature is replete with various systems and processes making use of high frequency power to achieve specific goals or results. For the most part, such prior art arrangements are designed to perform a specific task on a particular product. In general, such previous techniques have been quite costly, and in a number of instances have been comparatively inefficient.
As indicated above, a number of patents exist in which various attempts have been made to derive a specific result when using high frequency energy. For example, there is U.S. Pat. No. 3,611,582, issued on Oct. 12, 1971 to Michael A. Hamid et al for "Microwave Package for Control of Moisture Content and Insect Infestations of Grain." In the system described in this patent, a magnetron is employed as the microwave generator for directing microwave energy into a column of grain flowing downwardly through a waveguide. A flap valve at the lower end of the column controls the rate of descent of the grain. In one embodiment, a window pervious to microwave energy permits the microwave energy to be literally sprayed onto the downwardly flowing column of grain. In another embodiment, two such windows are utilized so as to introduce the microwave energy at two vertically spaced locations. Temperatures are sensed of the flowing grain and the flap valve at the bottom of the column of grain is adjusted so as to control the temperature by regulating the flow of grain. While the system is apparently more efficient than a number of patented arrangements, nonetheless, the use of a waveguide does not result in a high degree of absorption of the microwave energy. Also, the degree of control derived from the flap valve is only of a general character and is not as precise as would be required in the processing of many dielectric materials.
Even though a number of patents claim a high degree of efficiency, it should be borne in mind that the degree of efficiency is only relative. A rather complicated and costly apparatus is described in U.S. Pat. No. 4,330,946, granted on May 25, 1982 to Calice G. Courneya for "High Efficiency Material Drying." In the apparatus described in this patent, the efficiency is increased by reclaiming some of the heat that would otherwise be lost in the moisture that is removed. The efficiency is also enhanced by utilizing a vacuum drying chamber in which a bank of magnetrons is associated, some of the heat being reclaimed from the magnetrons and from the vapor containing the moisture that has been removed from the granular material. The microwave energy is literally sprayed toward the granular material as it is augered through what is termed in the patent as a primary chamber. While the patented apparatus is perhaps more efficient than some of the earlier processes, and the patentee stresses this, nevertheless, the patented apparatus is quite costly to manufacture, as explained above, and actually requires a significant amount of electrical energy to reclaim the heat, the reclaiming procedure being a principal objective of the patentee.